Cardinal O'Brien denies the allegations, saying he is stepping down to avoid causing damage to next month's papal election.

For latest we're joined by Europe correspondent Philip Williams, who's in London.

Philip, what is the nature of the allegations against Cardinal O'Brien?

PHILIP WILLIAMS, EUROPE CORRESPONDENT: Well they're not specific. They're rather general. They were publicised over the weekend in The Observer newspaper. But where were a couple of quotes from a couple of the four that have complainants.

One of them said he established - or there was established an inappropriate relationship with the cardinal requiring long-term counselling after that for him. Another described as an inappropriate approach after evening prayers when he was just 18.

Now of course the cardinal has denied all of this and he had been planning in the next 24 hours to travel to the Vatican to take part in the conclave. That's now not going to happen. And in the last few minutes, it's been announced that the Pope has accepted his resignation.

So it's a disaster for him personally. He's just a few weeks off retirement at 74, but now he'll have to still face these allegations and he will be asked about them by the Church in the Vatican and asked to give his side of the story.

EMMA ALBERICI: Is there any sense that this is connected to a wider story circulating in the Italian media implicating a bigger scandal within the Vatican?

PHILIP WILLIAMS: No, this seems quite a separate affair. It's come out of left field. We didn't expect this. Those other allegations, again, they've been denied by the media office attached to the Pope as being a reason for the pontiff's resignation, they've been circulating mainly in the Italian media. Stories of sexual impropriety, of corruption, of terrible back-biting within the Vatican.

But as I say, that's not - that's quite a separate issue to this issue involving the Scottish church.